Cutting oil composition



United States Patent CUTTING OIL COMPOSITION Everett C. Hughes, Shaker Heights, and Harrison Stine, Lyndhurst, Ohio, assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application December 30, 1955 Serial No. 556,409

1 Claim. (Cl. 25248.4)

The present invention relates to lubricating compositions. In particular, the invention relates to novel lubricating compositions which have particular utility in connection with ditficult machining operations.

Numerous lubricating compositions are known and used in industries conducting machining operations. A large number of such compositions are of the type known to the art as soluble oil lubricants. These lubricants usually comprise a mixture of a mineral oil and an emulsifying agent. Before use, such lubricants are emulsified in water and it is the water emulsion that is applied to the machines and work pieces during the machining operations. Lubricating compositions of this type are employed largely as coolants and only secondarily for their lubricating properties. Such lubricants possess wide utility in machining operations. Many metals may be machined without appreciable difficulty with the aid of such lubricants.

However, there are a number of machining operations which must be performed on materials which are not particularly amenable to such operations. In such machining operations, lubricating compositions of the soluble oil type are not completely satisfactory and do not give satisfactory lubrication. For example, in a machining operation on an abrasive metal the cooling of the cutting tool becomes secondary in importance to the lubrication of the tool which is in contact with the work piece. Consequently, a lubricant of the soluble oil type is not satisfactory and it is the practice in the art to employ a lubricant in such operations which is almost entirely oleaginous in nature and contains substantially no water. Such compositions are to be distinguished from the aforementioned soluble oil type inasmuch as they must meet quite different desiderata.

Typical of the compositions proposed by the prior art for the more diflicult machining operations as, for example, the machining of abrasive metals, are compositions comprising sulfurized hydrocarbon oils and lard oil, which is chiefly the triglyceride of oleic acid. Such compositions, while useful, have left much to be desired in terms of their ability to prolong the life of machine tools.

Accordingly, it is the object of the present invention to provide a lubricating composition which is an effective lubricant for machining operations on metals which are unusually diflicult to machine.

It is another object of this invention to provide a lubricating composition which will appreciably prolong the life of tools which are employed in difficult machining operations on metals such as abrasive steels and the like.

In brief, the lubricating compositions of the present invention comprise a sulfurized mineral oil and a fatty acid partial ester of a hexahydric alcohol.

A sulfurized oil base of the type contemplated herein is obtained by dissolving an amount of elemental sulfur in a mineral oil at elevated temperatures, i. e., 180 F. to 250 F. The mineral oil employed in the preparation of the sulfurized oil may be any hydrocarbon oil of lubricating viscosity and may be refined or unrefined. If the oil is to be refined, any of the conventional refining processes such as solvent extraction or acid treatment may be employed. The sulfur employed to sulfurize the oil may be any of the ordinary commercial varieties of elemental sulfur such as flowers of sulfur. The sulfurized oil base should contain 0.3 to 2.0% by Weight of sulfur for the purposes of this invention. Whether the sulfur reacts with the oil or not is immaterial, but it is in the solution, whether in physical or chemical combination, and is referred to in the art as dissolved sulfur. Such an oil is known in the artas a sulfurized oil. Compositions of the type contemplated herein may comprise between about 99 to weight percent of the sulfurized oil base.

The fatty acid partial ester of. a hexahydric alcohol of the type contemplated herein is prepared from a selected group of fatty acids. The hexahydric alcohol, may be sorbitol, mannitol, dulcitol, any isomers thereof. Reference to the alcohols includes the hydrates thereof. The fatty acid employed to esterify the alcohol is selected from the group of fatty acids lying between and including the acids containing 16 to 20 carbon atoms. The fatty acid may be either saturated or unsaturated. Examples of such fatty acids are palmitic, oleic, linoleic, linolenic, arachidic, arachic, arachidonic, or stearic acid. At least one of the hydroxy groups in the hexahydric alcohol must be esterified and at least one must not be esterified. Preferably, one to three hydroxy groups are esterified.

The compositions of our invention may include amounts ranging from 1 to 20% by weight of the esters described hereinabove. It has been found that an amount of the ester less than 1% will not produce a composition efiective for the purposes of this invention.

The lubricating compositions of our invention may also contain minor amounts of chlorinated extreme pressure additives, as for example, an oil soluble chlorinated organic compound having a chlorine content of at least 25% The amount of the chlorinated organic compound should be such as to provide A to 5% chlorine in the composition. Examples of such compounds are chlorinated aromatics such as chlorinated naphthalene, chlorinated diphenyl, chlorinated diphenyl oxide and chlorinated paraffin wax. Chlorinated compounds useful as E. P. additives are well known in the art. A number of chlorinated diphenyls are described in U. S. Patent No. 1,892,397 to R. L. Jenkins. A particularly useful additive is Arochlor 1254 which is a chlorinated diphenyl having a chlorine content of 54%, a specific gravity between 1.538 and 1.548 and a distillation range of 365-390 C As examples of our invention, the composition identified below as Examples A and B were prepared. The sulfurized mineral oil employed in Examples A and B was prepared by dissolving 0.8% by weight elemental sulfur in the form of flowers of sulfur in a conventionally refined (acid treated) neutral oil having a viscosity of 100 SSU at 100 F. Y

Example A Ingredient: Weight percent Sulfurized mineral oil 92. Sorbitan mono-oleate 5 Chlorinated diphenyl (Arochlor 1254) 3 (1.62% chlorine). Example B Sulfurized mineral oil 96. Sorbitan trilinoleate 1. Chlorinated diphenyl (Arochlor 1254) 3 (1.62% chlorine).

For purposes of comparison, a composition typical of the prior art compositions was prepared and is listed below as Example C. The sulfurized mineral oil of Example C was prepared from a conventionally refined mineral stock having a viscosity of 150 SSU at 100 F. and 1.25 weight percent sulfur.

chlorine.

In order to demonstrate the advantages to be derived from the compositions of our invention, a series of comparative tests were conducted employing the lubricants of Examples A and B under actual machine shop conditions. In one of these tests, the lubricants of Examples A and C were compared in the lubrication of a flute milling machine which was manufacturing /2" twist drills from Momax high-speed steel, a steel having 0.78 to 0.84 carbon, 3.5 to 4.0 chromium, 8.2 to 9.4 molybdenum, 1.3 to 2.0 tungsten, 1.0 to 1.3 vanadium, and the balance iron. It was possible to manufacture only 35 drills before it became necessary to replace the cutting tool when employing the lubricant of Example C. On the other hand, when employing the lubricant of Example A, it was found that 75 twist drills could be manufactured before it became necessary to replace the cutting tool. The fact that tool life was more than doubled with the lubricant of Example A is quite startling and it reflects an improvement in the lubricant of a very unusual degree.

In another of the tests, the lubricants of Example B and Example C were compared during the manufacture of '91 twist drills. This also was a flute milling operation and the milling stock was a diflerent but similar Momax high-speed steel. The average tool life when employing the lubricant of Example C as a lubricant was 46 drills. When the lubricant of Example B was employed in this operation, it was found that 67 drills could be produced before it became necessary to replace the cutting tool. The increase in tool life obtained with the lubricant of our invention was again surprising and unexpected.

Thus the utility and advantages of the lubricating compositions made in accordance with our invention have been demonstrated. Accordingly, we desire to obtain Letters Patent covering all the embodiments of our invention which will reasonably fall within the scope of the appended claim.

We claim:

A lubricating composition consisting essentially of a sulfurized mineral oil in an amount ranging from 80 to 99% by weight, a partial fatty acidester selected from the group consisting of sorbitan mono-oleate and sorbitan trilinoleate in an amount ranging from 1 to 20% by weight, and an oil-soluble chlorinated organic E. P. compound in an amount to provide from A to 5% chlorine by weight.

References Cited in the file of this patent UNITED STATES PATENTS 1,824,523 Adams Sept. 22, 1931 2,066,354 Lincoln Jan. 5, 1937 2,564,423 Barnum Aug. 14, 1951 2,689,222 Oathout Sept. 14, 1954 

